There is already known an image forming method, wherein a color image (hereinafter sometimes referred to as “color diffraction grating image”) including a diffraction grating is formed by transferring each diffraction grating onto a transferred medium from a transfer sheet in which plural diffraction gratings are formed, the diffracted lights of the plural diffraction gratings differ from one another in a particular observation direction (for example, see Patent Documents 1 and 2).
Patent Document 1: Japanese Patent Application Laid-Open No. H08-123299
Patent Document 2: Japanese Patent Application Laid-Open No. H09-272255